Metal filters have long been used for a variety of applications. For example, porous stainless steel filters prepared from sintered metal particulate, e.g., stainless steel powder, have been used in a variety of processes where high pressure drops are acceptable and in applications where relatively fine filtration capability must be combined with mechanical strength, resistance to high temperatures, and/or resistance to chemical attack. Such applications include the filtration of fine catalysts used in fluidized bed catalytic processes where elevated temperatures are encountered, e.g., fluid catalytic cracking processes, and in the manufacture of high fidelity recording tapes.
Still another use of such filters is in the filtration of molten resin used in the manufacture of polymeric films and fibers as, for example, polyester film.
Conventional sintered metal media suffer from variations in density in the process of laying the powder down prior to sintering. The present invention provides a method of powder laydown that results in very uniform filter performance.
In addition to a highly uniform filter performance, it is found that the products made by the process of the invention show a significant increase in efficiency and dirt holding capacity.